Claims are definitions or assertions made about a certain party or object.
- Some of these claims and their meaning are defined as part of the JWT spec. Others are user-defined.
 - The magic behind JWTs is that they standardize certain claims that are useful in the context of some common operations. For example, one of these common operations is establishing the identity of a certain party. So one of the standard claims found in JWTs is the sub (from “subject”) claim.